#include <userver/fs/fs_cache_client.hpp>

#include <boost/filesystem.hpp>
#include <boost/filesystem/operations.hpp>

#include <userver/engine/task/task_processor_fwd.hpp>
#include <userver/fs/read.hpp>
#include <userver/logging/log.hpp>
#include <userver/rcu/rcu_map.hpp>
#include <userver/utils/async.hpp>
#include <userver/utils/periodic_task.hpp>

USERVER_NAMESPACE_BEGIN

namespace {

std::string GetNormalizeDirectory(std::string_view dir) {
    auto slice = dir.size();
    // NOLINTNEXTLINE(modernize-loop-convert)
    for (auto it = dir.rbegin(); it != dir.rend(); ++it) {
        if (*it == '/') {
            --slice;
        } else {
            break;
        }
    }
    return std::string{dir.data(), slice};
}

}  // namespace

namespace fs {

#ifdef __linux__
namespace {

bool IsFilepathHidden(const std::string& path) {
    auto filename = boost::filesystem::path(path).filename().string();
    return filename[0] == '.';
}

}  // namespace
#endif  // __linux__

FsCacheClient::FsCacheClient(std::string_view dir, std::chrono::milliseconds update_period, engine::TaskProcessor& tp)
    : dir_(GetNormalizeDirectory(dir)),
      update_period_(update_period),
      tp_(tp)
{
    UpdateCache();

    if (update_period_ == std::chrono::milliseconds(0)) {
        return;
    }

#ifdef __linux__
    inotify_task_ = utils::CriticalAsync("inotify_task", [this] { InotifyWork(); });
#else
    cache_updater_.Start("fs_cache_updater", utils::PeriodicTask::Settings{update_period_}, [this] { UpdateCache(); });
#endif
}

void FsCacheClient::UpdateCache() {
    auto map = fs::ReadRecursiveFilesInfoWithData(tp_, dir_, {fs::SettingsReadFile::kSkipHidden});
    data_.Assign(std::move(map));
}

#ifdef __linux__
void FsCacheClient::InotifyWork() {
    namespace sys_linux = engine::io::sys_linux;
    sys_linux::Inotify inotify;

    HandleCreateDirectory(inotify, dir_);

    while (!engine::current_task::ShouldCancel()) {
        auto event = inotify.Poll({});
        LOG_INFO() << event;
        if (!event) {
            return;
        }

        if (event->mask & sys_linux::EventType::kMovedFrom || event->mask & sys_linux::EventType::kDelete) {
            if (!(event->mask & sys_linux::EventType::kIsDir)) {
                HandleDelete(event->path);
            } else {
                HandleDeleteDirectory(inotify, event->path);
            }
        }

        if (event->mask & sys_linux::EventType::kMovedTo || event->mask & sys_linux::EventType::kCreate ||
            event->mask & sys_linux::EventType::kModify)
        {
            if (!(event->mask & sys_linux::EventType::kIsDir)) {
                HandleCreate(event->path);
            } else {
                HandleCreateDirectory(inotify, event->path);
            }
        }
    }
}

void FsCacheClient::HandleDelete(const std::string& path) { data_.Erase(GetLexicallyRelative(path, dir_)); }

void FsCacheClient::HandleDeleteDirectory(engine::io::sys_linux::Inotify& inotify, const std::string& path) {
    LOG_INFO() << "HandleDeleteDirectory()";
    inotify.RmWatch(path);
}

void FsCacheClient::HandleCreate(const std::string& path) {
    if (IsFilepathHidden(path)) {
        return;
    }

    FileInfoWithData info{};
    info.extension = boost::filesystem::path(path).extension().string();
    info.data = ReadFileContents(tp_, path);
    data_.InsertOrAssign(GetLexicallyRelative(path, dir_), std::make_shared<const FileInfoWithData>(std::move(info)));
}

void FsCacheClient::HandleCreateDirectory(engine::io::sys_linux::Inotify& inotify, const std::string& path) {
    engine::AsyncNoSpan(tp_, [&] { return HandleCreateDirectoryBlocking(inotify, path); }).Get();
}

void FsCacheClient::HandleCreateDirectoryBlocking(engine::io::sys_linux::Inotify& inotify, const std::string& path) {
    LOG_INFO() << "HandleCreateDirectory(" << path << ")";
    namespace sys_linux = engine::io::sys_linux;
    inotify.AddWatch(
        path,
        {
            sys_linux::EventType::kModify,
            sys_linux::EventType::kMovedFrom,
            sys_linux::EventType::kMovedTo,
            sys_linux::EventType::kDelete,
            sys_linux::EventType::kCreate,
        }
    );

    for (auto it = boost::filesystem::directory_iterator(path); it != boost::filesystem::directory_iterator(); ++it) {
        if (is_directory(it->status())) {
            HandleCreateDirectoryBlocking(inotify, path + '/' + it->path().filename().string());
        } else {
            HandleCreate(path + '/' + it->path().filename().string());
        }
    }
}
#endif

FileInfoWithDataConstPtr FsCacheClient::TryGetFile(std::string_view path) const {
    LOG_DEBUG() << "Find file " << path;
    auto snap = data_.GetSnapshot();
    if (auto it = snap.find(std::string{path}); it != snap.end()) {
        return it->second;
    }
    return nullptr;
}

}  // namespace fs

USERVER_NAMESPACE_END
